[ImgBot] Optimize images

*Total -- 1,331.35kb -> 1,169.31kb (12.17%)

/screenshots/3.png -- 169.98kb -> 126.22kb (25.75%)
/screenshots/4.png -- 143.87kb -> 112.20kb (22.01%)
/screenshots/2.png -- 147.07kb -> 114.99kb (21.81%)
/public/images/registerCandidate.png -- 19.36kb -> 16.58kb (14.31%)
/screenshots/1.png -- 325.75kb -> 279.49kb (14.2%)
/public/images/manageEvent.jpg -- 67.09kb -> 63.89kb (4.77%)
/public/images/quest_logo.png -- 458.23kb -> 455.94kb (0.5%)

Signed-off-by: ImgBotApp <[email protected]>

Author: ImgBotApp